The electrical conductivity of NiO at 1000°C

Specimens of NiO for conductivity measurements were made from Ni foil, containing less than 25ppm total impurities, by spot welding platinum leads to the foil which was then oxidized to compact NiO at 1300°C. Four point d.c. conductivity measurements were carried out at oxygen partial pressures between 1 atm and 10^?10 atm provided by gas mixtures and monitored using a zirconia-based solid state cell sensitive to oxygen. The results indicate a predominance of doubly charged cation vacancies below 10^?5 atm oxygen partial pressure and of singly charged cation vacancies above this value.